1. Field of the Invention
This invention relates generally to prefabricated structural systems utilizing a plurality of side-by-side panels to provide a continuous fluid-tight membrane, and more specifically relates to such a structural system particularly suited for roofs of buildings, or other exterior or interior walls requiring a continuous fluid-tight membrane with superior structural strength, and good insulating and fire resistance properties adequate to meet building codes. In one of its aspects it relates to a joint assembly for sealing the intersection of two or more panels in the system to provide the fluid-tight membrane.
2. Description of the Prior Art
Conventional built-up roofing systems have been employed for many years. In this method of construction, a horizontal roof deck typically corrugated deck and insulation, planking or plywood, is supported on underlying structural beams. The entire roof deck is covered by a continuous weatherproof membrane usually comprising alternate layers of felt and bitumen to prevent penetration of moisture into the building interior. The membrane is applied in a field operation by application of alternate layers of hot or cold bitumen and felt. Once the membrane is applied to the desired thickness, gravel, rock or similar aggregate material is spread upon the roof to provide ballast to hold the roof down against wind generated uplift and protection against weathering. To reduce heat transfer through the roof deck, insulation is often applied to the underside of the roof deck at the interior of the building. Insulation may also be applied on the exterior of the roof deck and subsequently covered with the water resistance membrane and ballast rock.
There are many difficulties with built-up roof systems of the type described above. Since the construction of the built-up roof is entirely a field operation, there is little uniformity of quality from one building to another and consequently the integrity of such a roof structure varies considerably. A built-up roof membrane has a tendency to bubble and crack. This deterioration results from a number of factors including expansion and contraction from severe temperature changes, moisture trapped below the water resistant membrane, and improper construction techniques. Further, built-up roofs do not readily withstand heavy foot traffic and are susceptible to damage from traffic. Also considerable safety and environmental hazards exist in the application of hot tar which often gives off toxic fumes and polluting matter. Because of the undesirable nature of the hot tar process, local and federal safety and pollution standards often prohibit or restrict the use of built-up systems which formerly had wide acceptance.
In co-pending applications Ser. No. 336,370, filed Feb. 27, 1973, now U.S. Pat. No. 3,909,998, and Ser. No. 336,364, filed Feb. 7, 1973, both of which are assigned to the assignee of the present invention, both disclosures of which are hereby incorporated in this application by reference, a prefabricated panelized roofing system is described and claimed which employs Hypalon membrane panels having superior weathering characteristics as a top surface on prefabricated panels capable of spanning spaced substructural members. These panels include extruded Hypalon fasteners along the edges of the Hypalon membranes which can be engaged after the panels are arrayed in a roof structure and fastened to the underlying structure to form a continuous watertight membrane when the intersection of four sides is properly sealed. In order for such a system to be commercially successful, various governmental building code requirements, Underwriters Laboratory ratings, and manufacturers association ratings must be met. The panels must have the ability to withstand catastropic failure due to wind uplift, general load bearing ratings, fire ratings for both resisting and containing an interior fire, and for resisting flying embers from adjacent buring buildings. In addition, the panels must have a good U-factor, i.e., insulation rating. Because one face of each panel is exposed to the interior of a building, with a relatively stable temperature, while the other surface is an exterior surface of the building, the panel must be able to withstand relatively large, highly cyclical thermal stresses. In addition, such panels must be economical and repeatedly manufacturable on a production line and must require minimum field erection labor and skill. Such a system must also be erectable in adverse temperature and moisture conditions.
In co-pending United States patent application Ser. No. 624,587, filed Oct. 22, 1975, a panel system is disclosed which has high strength but light weight so that it can be manually lifted. The panels have superior weathering qualities, are reliably fluid-tight, and can be easily and quickly erected in a wide variety of weather conditions with minimum labor and skill. They also provide a strong and convenient platform for workmen during all states of erection, have good resistance to fire resulting from flying embers on the top surface, have superior insulating properties, can withstand extreme temperature cycling, have a relatively economically manufactured with a minimum capital investment and minimum transportation cost. The panels also serve as a stable, flat base for accessories and penetrations, and are high resistant to handling and erection damage.
In accordance with that invention, a prefabricated panel is provided which comprises a Hypalon membrane intimately bonded to a metal sheet by an epoxy adhesive. This combination provides a surface which has superior weathering characteristics and is highly resistant to most corrosive agents and is resistant to penetration by sharp objects, resists wear and deformation due to heavy foot traffic, and provides high tensile strength to resist wind uploads when the edges of the panel are fastened to a supporting structure. Extruded Hypalon fasteners bonded along the edges of the Hypalon membrane with a flexible web and extending over the edges of the panel which are fastened to the supporting structure provide a continuous waterproof membrane across adjacent panels except for the corner joints which is then sealed by means of a Hypalon putty material formed by dissolving Hypalon in a suitable solvent, such as toluene, which upon evaporation leaves a solid mass of Hypalon material bonded to the fastener halves and to the exposed surface of the Hypalon membrane. The solvent in the dissolved material also dissolves the surface of the Hypalon fasteners as well as the Hypalon membrane to provide an intimate bond, and the resulting mass of Hypalon is subsequently fixed by the radiation from the sun and finally by the passage of time to provide an integral chemical seal for the corner joint. Also, the ends of the joint between the fastener halves is exposed to ready access to the dissolved Hypalon material so that the ends of the capillaries extending along the length of the fastener grooves are sealed. Also, all other paths leading along the surfaces of the various overlapped layers of Hypalon materials are similarly sealed. As noted in that application, alternatively, a mechanical device can be used to compress a mastic into the area defined by the corner joint to seal the capillaries and form a peripheral surface dam.